On a computer apparatus, it is possible for users to perform an editing operation using an operating history, such as an operation to cancel a last operation so as to resume an original operation (hereinafter, called an “Undo”) and an operation to perform the canceled operation over again (hereinafter, called a “Redo”). Further, owing to the fact that a method for sequentially canceling previous operations one by one makes it difficult to efficiently perform the editing operation, proposed is such anther method that makes it possible to group a plurality of operating histories into a single group, so as to cancel the operations in a unit of the group.
For instance, Japanese Patent Application Laid-Open Publication (JPA) No 2009-151449 discloses an electronic blackboard having an “Undo” function. The electronic blackboard is provided with an inputting section that accepts various kinds of inputting and instructing operations, which are performed by handwriting characters and figures; a display section that displays the characters and figures above-inputted thereon, corresponding to the inputted positions of the characters and figures; a history data storage section that stores the characters and figures above-inputted as a history for every scratch of the pen, therein; a determining section that determines a processing to be implemented, based on the operations accepted; a grouping processing section that performs a processing for determining a group constituted by plural histories in regard to more than one scratch of the pen; a selecting section that responds to a predetermined operation so as to select any one of the groups above-determined; and an “Undo” processing section that follows the histories in regard to the characters and figures, which are displayed on the display section, in the reverse sequence, so as to resume the state before performing the inputting operation, wherein the “Undo” processing section follows the histories in regard to only the group, selected by the selecting section, in a reverse sequence, so as to resume the display status before performing the inputting operation in regard to the group concerned.
As above-mentioned, in such a case that a single user operates a terminal device, it is possible for the user to conduct editing operations by cancelling the last operation, performing the cancelled operation over again, and cancelling the operations in a unit of a group, and so on, so as to realize the editing status desired by the user concerned.
In recent years, employed is an electronic conferencing system in which a plurality of terminal devices are coupled to each other so as to reflect operations performed on a screen of each terminal device onto another screen of the other terminal device, and a plurality of users performs operations onto a screen of a single terminal device so as to make discussions between them. In such the electronic conferencing system having the common working area in which a plurality of users commonly performs operations, sometimes, there arises such a need for editing only the operations performed by the specific user.
However, in such a case that the operations performed by a plurality of users are mingled with each other, the conventional method for sequentially undoing or redoing the operations one by one cannot make it possible to edit only the operations performed by the specific user. Further, according to the method disclosed in JP-A No. 2009-151449 aforementioned, since all of the operations included in the group are to be cancelled, operations performed by the other users are also cancelled at a time, when the operations performed by the other users are mingled within the same group. The present invention seeks to solve the problem.